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/**
* Copyright (C) 2023-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <memory>
#include "mongo/executor/network_interface.h"
#include "mongo/executor/scoped_task_executor.h"
#include "mongo/executor/task_executor.h"
namespace mongo::executor {
/**
* Implementation of a TaskExecutor that provides the ability to schedule RPC/networking on the same
* underlying network connection. The PinnedTaskExecutor is constructed from another TaskExecutor,
* and uses that TaskExecutor's ThreadPool and NetworkInterface/networking reactor to perform work.
* Specifically:
* - Functions that schedule work or manage events that happen locally, without going over the
* network, are passed-through to the underlying TaskExecutor (i.e. scheduleWork,
* makeEvent, waitForEvent).
* - Functions that involve scheduling RPC/networking are all run on the same underlying
* network-connection (i.e. TCP/Unix Domain Socket).
* Note that this means that the PinnedConnectionTaskExecutor can only speak to one host over its
* entire lifetime! If you need to speak to a different host, you need a different connection, so
* construct a *new* PinnedCursorTaskExecutor from the underlying executor.
*
* Certain methods are illegal to call. startup() is illegal to call because the TaskExecutor
* passed to PinnedConnectionTaskExecutor should be started-up prior to this object's construction,
* and no additional startup is needed.
* Additionally, diagnostic and network management methods:
* - appendDiagnosticBSON()
* - appendConnectionStats()
* - dropConnections()
* - appendNetworkInterfaceStats()
* are illegal to call because this TaskExecutor provides a distinct networking API. Gather
* diagnostics from the underlying TaskExecutor instead if needed.
*
* This type uses ScopedTaskExecutor to proxy work to the underlying TaskExecutor it is
* constructed from. This means that shutdown() and join() address only tasks dispatched
* through this executor, rather than passing through to the underlying executor.
*
* Note! The executor that this PinnedConnectionTaskExecutor is constructed from _must_
* out-life it - i.e. this PinnedConnectionTaskExecutor must be shutdown and joined
* before the underlying executor is. This is because this type must have access
* to the underlying thread pool to complete cancellation tasks as it shuts down.
*
* Exhaust commands are not supported at this time.
*/
class PinnedConnectionTaskExecutor final : public TaskExecutor {
PinnedConnectionTaskExecutor(const PinnedConnectionTaskExecutor&) = delete;
PinnedConnectionTaskExecutor& operator=(const PinnedConnectionTaskExecutor&) = delete;
public:
// The provided NetworkInterface should be owned by the provided TaskExecutor, and
// must outlive this type.
PinnedConnectionTaskExecutor(const std::shared_ptr<TaskExecutor>& executor,
NetworkInterface* net);
~PinnedConnectionTaskExecutor();
// Startup is illegal to call, as the provided executor should already be started-up.
void startup() override;
void shutdown() override;
void join() override;
SharedSemiFuture<void> joinAsync() override;
bool isShuttingDown() const override;
// These pass-through to the underlying TaskExecutor.
Date_t now() override;
StatusWith<EventHandle> makeEvent() override;
void signalEvent(const EventHandle& event) override;
StatusWith<CallbackHandle> onEvent(const EventHandle& event, CallbackFn&& work) override;
void waitForEvent(const EventHandle& event) override;
StatusWith<stdx::cv_status> waitForEvent(OperationContext* opCtx,
const EventHandle& event,
Date_t deadline) override;
StatusWith<CallbackHandle> scheduleWork(CallbackFn&& work) override;
StatusWith<CallbackHandle> scheduleWorkAt(Date_t when, CallbackFn&& work) override;
// This type provides special connection-pinning behavior for RPC functionality here.
StatusWith<CallbackHandle> scheduleRemoteCommandOnAny(
const RemoteCommandRequestOnAny& request,
const RemoteCommandOnAnyCallbackFn& cb,
const BatonHandle& baton = nullptr) override;
StatusWith<CallbackHandle> scheduleExhaustRemoteCommandOnAny(
const RemoteCommandRequestOnAny& request,
const RemoteCommandOnAnyCallbackFn& cb,
const BatonHandle& baton = nullptr) override;
// When cancel() is passed a CallbackHandle that was returned from schedule{Work}()/onEvent(),
// cancellation is passed-through to the underlying executor. If the CallbackHandle was returned
// from scheduleRemoteCommand then the executor will cancel the RPC attempt.
void cancel(const CallbackHandle& cbHandle) override;
// Wait is unimplemented at this time.
void wait(const CallbackHandle& cbHandle,
Interruptible* interruptible = Interruptible::notInterruptible()) override;
// Illegal to call because the view does not track it's portion of the underlying TaskExecutor's
// resources.
void appendConnectionStats(ConnectionPoolStats*) const override;
void appendNetworkInterfaceStats(BSONObjBuilder&) const override;
void appendDiagnosticBSON(BSONObjBuilder*) const override;
void dropConnections(const HostAndPort&) override;
bool hasTasks() override;
private:
// Ensures _stream is initialized with a valid LeasedStream to `target`.
// If we already have a _stream when this function is called, ensures the
// remote is `target` and returns a ready-future. Otherwise asynchronously
// initailizes _stream and returns a future that resolves once _stream is ready.
ExecutorFuture<void> _ensureStream(WithLock,
HostAndPort target,
Milliseconds timeout,
transport::ConnectSSLMode sslMode);
// Start processing pending/queued RPCs.
void _doNetworking(stdx::unique_lock<Latch>&&);
// CallbackState for RPCs. Non-RPC callbacks use the CallbackState from the _underlyingExecutor.
class CallbackState;
// Invoke the RPC and return a future of its response.
Future<RemoteCommandResponse> _runSingleCommand(RemoteCommandRequest command,
std::shared_ptr<CallbackState> cbState);
void _shutdown(WithLock);
// Alias for an RPC request and the associated CallbackState.
using RequestAndCallback = std::pair<RemoteCommandRequest, std::shared_ptr<CallbackState>>;
// Helper to cancel a CallbackState from this executor.
void _cancel(WithLock, CallbackState*);
// Helper that walks the _requestQueue in-order, completing any canceled callbacks, until
// it finds the first uncanceled one (if any), which it returns.
boost::optional<RequestAndCallback> _getFirstUncanceledRequest(stdx::unique_lock<Latch>&);
// Synchronizes access to the _requestQueue, _stream, and _isDoingNetworking variables, as well
// as all CallbackState members.
mutable Mutex _mutex;
ScopedTaskExecutor _executor;
// Owned by the TaskExecutor backing _executor above. Since ScopedTaskExecutor keeps a
// shared_ptr to it's backing TaskExecutor, _net will remain valid for at least the lifetime of
// _executor.
NetworkInterface* _net;
// This is the same executor that the ScopedTaskExecutor above provides a view over. We keep
// a pointer to it so that we can run cancellation tasks even after the ScopedTaskExecutor
// is shut down. This should _only_ be used to guarantee cancellation tasks will run, even
// after shutdown is called on this type!
std::shared_ptr<TaskExecutor> _cancellationExecutor;
// Queue of pending/not-yet-started RPC requests and corresponding completion callbacks
// scheduled on this executor.
std::deque<RequestAndCallback> _requestQueue;
stdx::condition_variable _requestQueueEmptyCV;
// Pinned-connection leased from _underlyingNet to run all RPCs through this executor.
// Initialized upon the execution of the first scheduled RPC, and subsequently re-used for all
// RPCs scheduled through this executor.
std::unique_ptr<NetworkInterface::LeasedStream> _stream;
bool _isDoingNetworking{false};
std::shared_ptr<CallbackState> _inProgressRequest;
enum class State { running, joinRequired, joining, shutdownComplete };
State _state = State::running;
};
} // namespace mongo::executor
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